It may be desirable to provide two types of fuel to an engine or to supply a single type of fuel via different fuel paths that provide different advantages and/or disadvantages. For example, during some conditions it may be desirable to operate an engine with gasoline while during other conditions it may be desirable to operate the engine with a gaseous fuel such as compressed natural gas (CNG). Alternatively, it may be desirable to supply an engine with two fuels that have different octane levels so that higher octane fuel may be conserved for high load conditions and less expensive low octane fuel can be used during low load conditions. A system where two fuels or fluids are injected to an engine may offer the most flexibility when separate injectors are provided for each fuel at each cylinder.
However, doubling a number of injectors supplying fuel to an engine can increase the cost and complexity of an engine controller and may not be feasible in some cases because of packaging constraints. One way to overcome controller packaging limitations and supply two fuels to an engine is to place a secondary controller in electrical communication with a first or primary controller. In this arrangement, the secondary controller can provide outputs to control the secondary fuel system.
One way to place the secondary controller in electrical communication with the primary controller is for the secondary controller to monitor primary controller outputs for each primary fuel injector that the primary controller is operating. The secondary controller can provide outputs to control secondary fuel injectors based on the outputs for the primary fuel injectors. For example, where the primary fuel injected is gasoline and the secondary fuel injected is CNG, fuel injector outputs of the secondary controller can be adjusted proportionately with the fuel injector outputs of the primary controller that are monitored by the secondary controller so as to provide a desired engine air-fuel ratio. Although such a system may be functional, it may require numerous electrical connections between the primary and secondary controllers. Further, such a system may not be as beneficial when it is desirable to inject two fuels to the engine during a single engine cycle since outputs to the secondary fuel injector are tied to outputs driving the primary fuel injectors.
The inventors herein have recognized the above-mentioned disadvantages and have developed an engine system, comprising: a first group of fuel injectors; a second group of fuel injectors; a serial communication bus; a first controller including instructions for directly driving the first group of fuel injectors and supplying commands via the serial communication bus to operate the second group of fuel injectors; and a second controller including instructions for receiving the commands via the serial communication bus and directly driving the second group of fuel injectors.
By communicating fuel injector pulse width for a plurality of fuel injectors over a sole asynchronous serial communication bus (e.g., a CAN bus), it may be possible to reduce a number of electrical connections between two controllers that each directly control separate groups of fuel injectors. For example, when multiple fuel pulse widths can be transmitted between two or more controllers over a single wire pair serial communication bus, a number of electrical connections may be reduced from n to 1, where n is a number of fuel injectors in the engine system.
Further, when fuel injector pulse widths are properly sent over a serial communication bus, fuel injectors controlled via a first controller may be operated differently than fuel injectors controlled via a second controller. For example, where a first fuel injector supplies gasoline to a cylinder and a second fuel injector supplies alcohol to the same cylinder, the first controller may directly operate the first fuel injector at a first fuel pulse width, and the second controller may directly operate the second fuel injector at a second pulse width. In this way, fuel injectors may be operated differently even though commands for both groups of fuel injectors originate from the first controller.
The present description may provide several advantages. Specifically, the approach may reduce wiring and system complexity where two injectors supply fuel to a single cylinder of an engine. In addition, the approach may reduce system cost since a controller originally designed to control supply of a single fuel to an engine can be converted to operate an engine with two fuels by simply electrically coupling a second controller to a serial communication bus of the first controller. Further, the approach may reduce system development time since instructions for operating fuel injectors may be integrated with existing instructions of a controller designed to control injection of a single fuel.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.